Susie Dai, a researcher at Mizzou, recently created a modified strain of algae designed to capture harmful microplastics from contaminated water. Her long term goal is not only to clean waterways but also to recycle the collected plastic into safer bioplastic materials, including composite plastic films.

"Microplastics are pollutants found almost everywhere in the environment, such as in ponds, lakes, rivers, wastewater and the fish that we consume," Dai, a professor in the College of Engineering and principal investigator at the Bond Life Sciences Center, said. "Currently, most wastewater treatment plants can only remove large particles of plastic, but microplastics are so small that they slip through and end up in drinking water, polluting the environment and harming ecosystems."

Engineered Algae Targets Microplastics

In a recent study, Dai used genetic engineering to develop algae that produce limonene, a natural oil responsible for the familiar scent of oranges.

The limonene changes the algae's surface properties, making it repel water. Since microplastics are also water repellent, the particles naturally stick to the algae when they meet in water. The process forms clumps that sink to the bottom, creating a dense biomass layer that can be collected and removed more easily.

The modified algae also grow in wastewater, where they absorb excess nutrients while helping clean the water during the process.

"By removing the microplastics, cleaning the wastewater and eventually using the removed microplastics to create bioplastic products for good, we can tackle three issues with one approach," Dai said. "While our research is still in the early stages, our eventual goal is to integrate this new process into existing wastewater treatment plants so cities can clean their water more effectively and reduce pollution while creating useful products at the same time."

Plans To Scale Up the Technology

Dai's lab already grows algae inside large tank bioreactors. One system, a 100 liter bioreactor nicknamed "Shrek," is currently used to process industrial flue gas as part of efforts to reduce air pollution.

Looking ahead, Dai hopes to create larger versions of the Shrek system that could eventually be adapted for wastewater treatment and the removal of other pollutants.

The study, "Remediation and upcycling of microplastics by algae," was published in Nature Communications.